Nonaqueous electrolyte secondary batteries, particularly lithium secondary batteries, have a high energy density and are thus in wide use as batteries for, for example, personal computers, mobile telephones, and portable information terminals. Such nonaqueous electrolyte secondary batteries have recently been developed as on-vehicle batteries.
Patent Literature 1, for example, discloses a nonaqueous electrolyte secondary battery including a polyolefin porous film whose ratio of a TD critical load distance measured in a scratch test to a MD critical load distance measured in a scratch test falls within a certain range.